This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: P-type ATPases comprise a large superfamily of proteins, present in both prokaryotes and eukaryotes, that transport inorganic cations and possibly other substrates across cell membranes. Based on phylogenetic studies they have been classified into 5 subfamilies, termed P1-P5, which group according to sequence similarities, transmembrane organization, and substrate specificity. The most poorly understood P-type ATPases are those of the P5 subfamily, which are expressed only in eukaryotes. The overall goal of the current proposal is to obtain basic information about the P5-ATPases in mice that will be essential for an eventual understanding of their cell biological and physiological functions. The aims of the current proposal are to 1) isolate full-length cDNA clones for each of the family members and determine their tissue distribution and membrane location, 2) overexpress the novel P-type ATPases in the appropriate cell lines in order to assess their ion specificity, and 3) determine their cellular and physiological roles in vivo using RNA interference (RNAi) and gene targeting technologies.